What Is Dew?

Every walk outside in the morning and see that the grass is all wet, even though it didn't rain? The water comes from the dew that formed overnight. In the night hours, air temperature usually cools down. Everything in nature cools at a different speed, but usually plants don't need a lot of time to drop in temperature. The cooler air around these things causes condensation (water) to form on their surface. This is the dew we see shining on the grass in the early morning hours.

The noun 'dew' means the small drops of water (dewdrops) which can be found on cool surfaces, such as grass, in the early morning. This is the result of atmospheric vapour condensing (reducing to liquid) on these surfaces in the colder night air. The temperature at which this condensation starts to take place is called dew point.
The word 'dew' is often used poetically to suggest freshness, moisture or even innocence in phrases such as 'dewy-eyed.' Occasionally the verb form 'to bedew' is used ('her pillow was bedewed with tears') but this is old-fashioned and very rare.

Dew is moisture witch develops over night.

They are water droplets, which is formed after the condensation of the water vapor from the sky over the night.